I never, ever fix a bug, even from another user, unless I can say
with some surety that I can see the circumstances that led to that
person writing that bug. It may be as simple as “oh, copy and paste
error” or “this person was tired and overlooked this edge case, and
that didn’t come up until now.” But if you see a bug and think, “How
in the hell did this code ever work?” then you’ve got a lot more
work to do (assuming the code did ever work), because you aren’t
allowed to move on until you can answer that question.

Understanding your code, and the underlying code of the environment
you’re in, is more important than fixing any one bug.